These CMOS key encoders provide all the necessary logic to fully encode an array of SPST switches The keyboard scan can be implemented by either an external clock or external capacitor These encoders also have on-chip pullup devices which permit switches with up to 50 kX on resistance to be used No
Features
Y Y Y Y Y Y Y Y Y
50 kX maximum switch on resistance On or off chip clock On-chip row pull-up devices 2 key roll-over Keybounce elimination with single capacitor Last key register at outputs TRI-STATE outpust LPTTL compatible Wide supply range Low power consumption
3V to 15V
Connection Diagrams
Pin Assignment for Dual-In-Line Package Pin Assignment for SOIC Pin Assignment for DIP and SOIC Package
TL F 6037.
MM54C922 MM74C922 16-Key Encoder MM54C923 MM74C923 20-Key Encoder
July 1993
MM54C922 MM74C922 16-Key Encoder MM54C923 MM74C923 20-Key Encoder
General Description
These CMOS key encoders provide all the necessary logic to fully encode an array of SPST switches The keyboard scan can be implemented by either an external clock or external capacitor These encoders also have on-chip pullup devices which permit switches with up to 50 kX on resistance to be used No diodes in the switch array are needed to eliminate ghost switches The internal debounce circuit needs only a single external capacitor and can be defeated by omitting the capacitor A Data Available output goes to a high level when a valid keyboard entry has been made The Data Available output returns to a low level when the entered ke
MM74C922 Datasheet
